DCC filling the filesystem

Chris Gleba chris@soma.978.org
Fri Nov 22 04:55:23 UTC 2002


This is probably not it but worth a check and nonetheless is a somewhat
amusing story:

When I was doing some consultant work for a company they had a similar
problem:  errors would occur that the disk was full but whenever I
looked at it, it had plenty of free space. . .it turns out that the
person who initially set up the system was inept and left /var on the
root partition and accidentally deleted /dev/null.  Thus, suid programs
that wrote to the special file /dev/null would create a regular file
called /dev/null and append to it and the next program that came along
would create a new /dev/null file and append to it -- thus the disk
usage varied dramatically in short periods of time (took me a while to
figure that one out).

Moral of the story, if you have a combination of /var with /dev, or /tmp
on the root partition very odd things like the scenario above will
happen. . . I doubt that that is the case, though. . .


On Thu, 2002-11-21 at 23:34, Vernon Schryver wrote:
> > From: Gary Mills <mills@cc.UManitoba.CA>
> 
> . ...
> > I'm seeing regular complaints that dcc's filesystem is full, yet there's
> > a gigabyte of space left...
> >
> > Nov 21 21:55:21 electra ufs: [ID 213553 kern.notice] NOTICE: realloccg /var/dcc: file system full
> > ...
> 
> That looks like a message from the kernel and not from any DCC
> code.  Thus, the UNIX kernel thinks the file system is full at
> least some of the time.
> 
> I see these possible explanations:
> 
>    1. the kernel is confused or the file system is corrupt.
>    2. when the various error messages happen, the file system is full.
>       2a. big files exist when the 22 to 137 MByte DCC files are being 
>           shuffled around
>       2b. the files are not really in /var/dcc
> 
> Have I missed anything?
> 
> #1 might be pursued by running `fsck` on the filesystem.
> 
> I don't see how #2b might happen.  Still, it wouldn't hurt to
> try `cd /usr/local/dcc; df -k .`
> 
> I would investigate #2a by looking at things while dbclean is
> running.  That can be done by running the /usr/local/dcc/libexec/cron-dccd
> script in one X window or rlogin/ssh/whatever shell while using
> `ls -la`, `df`, and `du` in another.
> 
> 
> Vernon Schryver    vjs@rhyolite.com
> _______________________________________________
> DCC mailing list      DCC@rhyolite.com
> http://www.rhyolite.com/mailman/listinfo/dcc
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